The present invention relates to an auxiliary machine drive system of an automatic engine stop-restart system equipped automotive vehicle, and specifically to the improvement of an auxiliary machine drive system employing an electromagnetic clutch interposed between an engine and automotive auxiliary machines.
In recent years, there have been proposed and developed so-called idle-stop vehicles in which an engine is automatically stopped when the vehicle is in its stopped state for exhaust-emission reducing purposes, for example during the temporarily stopped state of the vehicle at a street intersection, and automatically restarted from the vehicle stand-still state. Idle-stop vehicles generally use an auxiliary machine drive system for subsidiarily driving auxiliary machines or car accessories for example a water pump of an engine""s cooling system, an air-conditioner compressor, a power-steering pump and the like. One such auxiliary machine drive system of a so-called idle-stop vehicle has been disclosed in Japanese Patent Provisional Publication No. 2001-193516 (herein after is referred to as xe2x80x9cJP2001-193516xe2x80x9d). In the auxiliary machine drive system disclosed in JP2001-193516, auxiliary machines such as a water pump of an engine""s cooling system, an air-conditioner compressor, and a power-steering pump, are connected to each of the engine and an auxiliary-machine drive motor via at least one power-transmission belt. In order to disconnect the engine (exactly, the engine crankshaft) from the auxiliary-machine drive system when driving the auxiliary machines by means of the drive motor and thus to reduce a load on the drive motor, an electromagnetic clutch is interposed between the engine and the auxiliary machines. In case of the system of JP2001-193516, when the engine is running, the electromagnetic clutch is energized for clutch engagement, and as a result the auxiliary machines are driven by means of the engine. Conversely when the engine is stopped, the electromagnetic clutch is de-energized for clutch disengagement, and as a result the auxiliary machines are driven by means of the drive motor in the presence of driving requirement for the auxiliary machines.
In a so-called idle-stop vehicle as disclosed in JP2001-193516, the engine is automatically temporarily stopped only when a specified condition, such as a zero vehicle speed, a depressed brake pedal, an adequate state of charge of the car battery, an automatic-transmission selector lever kept in a neutral position, and the like, is satisfied. In other words, except for the specified condition, the engine is conditioned in the running state. According to the system disclosed in JP2001-193516, the electromagnetic clutch remains energized during the engine running state. On the contrary, in the automatically-stopped state of the engine, i.e., under the specified condition, the electromagnetic clutch is kept in the deenergized state. As a matter of course, a time interval during which the clutch is energized tends to be remarkably longer than a time interval during which the clutch is deenergized. This results in an increase in electric power consumption, and consequently an increase of overall fuel consumption.
Accordingly, it is an object of the invention to provide an auxiliary machine drive system of an automatic engine stop-restart system equipped automotive vehicle, which is capable of remarkably shortening an energizing time for an electromagnetic clutch interposed between an internal combustion engine and automotive auxiliary machines and of reducing electric power consumption and overall fuel consumption.
In order to accomplish the aforementioned and other objects of the present invention, an auxiliary machine drive system of an automatic engine stop-restart system equipped automotive vehicle capable of automatically stopping or restarting an engine depending on vehicle operating conditions, comprises an electromagnetic clutch disposed between the engine and at least one auxiliary machine for connecting and disconnecting a crankshaft of the engine to and from the auxiliary machine, an electromagnetic clutch control unit deenergizing the electromagnetic clutch at least when the engine is running, and energizing the electromagnetic clutch only when a predetermined energizing condition is satisfied, the predetermined energizing condition including at least a stopped state of the engine, and the electromagnetic clutch comprising a normally-engaged electromagnetic clutch that is engaged when deenergized, and disengaged when energized.
According to another aspect of the invention, an auxiliary machine drive system of an automatic engine stop-restart system equipped automotive vehicle capable of automatically stopping or restarting an engine depending on vehicle operating conditions, comprises a motor generator connected to at least one auxiliary machine to drive the auxiliary machine, the motor generator serving as an engine start-up motor that is connected to a crankshaft of the engine via the electromagnetic clutch when automatically restarting the engine, an electromagnetic clutch disposed between the engine and each of the auxiliary machine and the motor generator for connecting and disconnecting the crankshaft of the engine to and from each of the auxiliary machine and the motor generator, a wrapping connector by which the auxiliary machine and the motor generator are directly connected to each other, an electromagnetic clutch control unit deenergizing the electromagnetic clutch at least when the engine is running, and energizing the electromagnetic clutch only when a predetermined energizing condition is satisfied, the predetermined energizing condition including at least a stopped state of the engine, and the electromagnetic clutch comprising a normally-engaged electromagnetic clutch that is engaged when deenergized, and disengaged when energized.
According to a further aspect of the invention, an auxiliary machine drive system of an automatic engine stop-restart system equipped automotive vehicle capable of automatically stopping or restarting an engine depending on vehicle operating conditions, comprises an electromagnetic clutch disposed between the engine and at least one auxiliary machine for connecting and disconnecting a crankshaft of the engine to and from the auxiliary machine, a control means for deenergizing the electromagnetic clutch at least when the engine is running, and for energizing the electromagnetic clutch only when a predetermined energizing condition is satisfied, the predetermined energizing condition including at least a stopped state of the engine, and the electromagnetic clutch comprising a normally-engaged electromagnetic clutch that is engaged when deenergized, and disengaged when energized.
According to a still further aspect of the invention, a method for executing automatic engine stop-restart control functions for an auxiliary machine drive system of an automatic engine stop-restart system equipped automotive vehicle capable of automatically stopping or restarting an engine depending on vehicle operating conditions and having an electromagnetic clutch disposed between the engine and at least one auxiliary machine for connecting and disconnecting a crankshaft of the engine to and from the auxiliary machine and a motor generator connected to the auxiliary machine to drive the auxiliary machine, the method comprises determining whether a specified automatic stop condition of the engine is satisfied, automatically stopping the engine when the specified automatic stop condition of the engine is satisfied, determining whether a requirement for driving the auxiliary machine by means of the motor generator is present, energizing and disengaging the electromagnetic clutch when the specified automatic stop condition of the engine is satisfied and the requirement for driving the auxiliary machine by means of the motor generator is present, driving the auxiliary machine by means of the motor generator when the electromagnetic clutch is energized and disengaged when the specified automatic stop condition of the engine is satisfied and the requirement for driving the auxiliary machine by means of the motor generator is present, determining whether a specified-automatic restart condition of the engine is satisfied, deenergizing and engaging the electromagnetic clutch when the specified automatic restart condition of the engine is satisfied, and automatically restarting the engine by driving the crankshaft by means of the motor generator and by cranking the engine when the specified automatic restart condition of the engine is satisfied.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.